1. Field of the Invention
The present invention relates to a TV phone apparatus and a control method therefor.
2. Description of the Related Art
In comparison with a conventional voice telephony apparatus only for making a voice phone conversation, a common TV phone apparatus requires a faster data transmission rate because of the larger amount of transmission at the time of a phone conversation. Furthermore, when a sufficient data transmission rate cannot be obtained because of the radio wave condition, problems are caused, such as disturbance of images displayed on the TV phone apparatus and disconnection of a phone conversation.
In comparison, JP2001-274742A and JP2004-32804A disclose techniques in which, when the data transmission rate becomes below a predetermined value, transmission and reception of video image data are stopped, and only a voice phone conversation by voice data is made.
Recently, attention has been focused on 3-D video image techniques such as a 3-D camera that takes a three-dimensional stereoscopic video image (hereinafter referred to as a 3-D video image) and a 3-D display that displays a 3-D video image.
The 3-D display causes a viewer to visually confirm a three-dimensional stereoscopic video image by displaying multiple video images with different parallaxes in turn or by displaying multiple video images with different parallaxes at the same time by changing the display angle. The 3-D camera is provided with multiple image-taking means, and takes multiple video images with different parallaxes as a 3-D video image using each of the image-taking means.
As a technique in which a 3-D video image technique is applied to a TV phone apparatus, there is a camera-equipped mobile information terminal described in JP2010-141447A. This camera-equipped mobile information terminal makes it possible to make a phone conversation with a phone conversation counterpart while seeing a 3-D video image, by transmitting 3-D video image data indicating a 3-D video image taken by a 3-D camera in real time together with voice data.
However, in a 3-D TV phone apparatus that transmits 3-D video image data like the camera-equipped mobile information terminal described in JP2010-141447A, it is necessary to cause the multiple image-taking means to operate at the same time, perform video image processing on multiple video image signals and increase the frame rate of the display image.
Therefore, in the 3-D TV phone apparatus, the amount of the operation of internal devices, such as a camera, a display and a CPU (Central Processing Unit), increases in comparison with a conventional 2-D TV phone apparatus that transmits a two-dimensional plane video image (hereinafter referred to as a 2-D video image), and, consequently, noise caused in the internal devices increases.
The transmission rate at the time of a phone conversation is influenced by noise. Therefore, when noise caused in the internal devices increases, a problem occurs that, especially in an environment with a bad radio wave condition, a sufficient data transmission rate cannot be obtained, and a phone conversation is easily disconnected.
In the techniques described in JP2001-274742A, JP2004-32804A and JP2010-141447A, the increase in noise due to a 3-D TV phone apparatus is not considered, and the above problem cannot be solved.